Heavy metals such as mercury, lead, cadmium and silver can bind to proteins on the proteins' incorporated cysteine residues which contain sulfhydryl or —SH groups. This abnormally inhibits or activates their biological properties. Further, a heavy metal binding specific proteins can induce damage that leads to overproduction or leakage of reactive oxygen species (ROSs) from their normal locations. These ROSs, mostly produced in the mitochondria of the cells of the body, then react with protein, nucleic acid (DNA, RNA) and lipid molecules in the healthy cell changing their property/chemistry and leading to unhealthy cells that may die or at least be unable to defend themselves from other stress factors such as viral infection. In addition to heavy metals there are many other chemical toxicants that can induce oxidative stress including, for example, radiation toxicity, acetominophen and dioxin. Further, it is well known that the oxidation of reduced glutathione (GSH) to oxidized glutathione (G-S—S-G) is one of the first biochemical signals for apoptotic cell death (or programmed cell death). The inadvertent oxidation of GSH by toxin produced ROSs could lead to increased GSSG and cell death also. In the healthy body GSH accomplishes protection against heavy metal toxicity, organic toxins and hydroxyl free radical damage due to its chemical ability to; (1) chelate heavy metals, (2) its use by the enzyme glutathione-S-transferase (GST) to produce GS-toxin complexes that are actively removed from the intracellular location into the blood and then actively removed from the blood by GS-toxin receptors in the bilary transport system of the liver and into the bile and feces and (3) GSH's ability to scavenge and eliminate hydroxyl free radicals.
It is well known that excess exposures to heavy metals, above the capacity of the normal cellular GSH capability to bind and remove, inhibit the enzymes involved in the synthesis of GSH and the recovery of oxidized GSH from GSSG (oxidized glutathione) leading to decreased GSH levels that are identified as oxidative stress. Also, such heavy metal excesses lead to an overproduction of free radicals by the mitochondrial and further oxidizes GSH to GSSG and decreases the cells ability to remove toxins (organic and heavy metals) by the lowering of the intracellular concentration of GSH. Therefore, an ideal way to recover GSH levels would be to develop a non-toxic compound with membrane penetrating abilities, heavy metal binding properties and reactive oxygen species scavenging properties that were superior to GSH.
With these properties a well designed compound with both heavy metal chelation properties and antioxidant properties could; (1) easily penetrate cell membranes and the blood brain barrier, (2) bind heavy metals preventing their inhibition of enzymes needed to synthesize GSH and recover GSH from GSSG, (3) decrease free radical formation by reversing heavy metal inhibition of the mitochondrial electron transport system, and (4) scavenge hydroxyl free radicals preventing oxidation of naturally produced GSH to GSSG. With these four properties such a compound could dramatically increase intracellular GSH and reduce free radical damage and allow the cells to recover to a normal state. In addition, the increase in intracellular GSH would allow GST to remove organic toxins built up during periods of toxicity and enhance the ability of the P-450 system to further detoxify the subject using the natural system. For example, it is well known that GSH is directly involved in binding to components of viral replication systems inhibiting viral replication. Low GSH levels are a major risk factor for several viral infections and high GSH seems involved in reversing and preventing such viral infections.
In order to medically prevent or reduce the oxidative stress problem identified as low GSH levels, heavy metals must be excreted by natural means or complexed by medically based chelator compounds that render them biologically unavailable to elicit their toxic effects. To effect this removal and tightly bind the heavy metals, the treating compound must be able to effectively remove the metal from the single sulfur residue and bind it more tightly than is capable with only one sulfur to metal bond. That is, the compound must make at least two intramolecular sulfur to metal bonds to be able to prevent subsequent reaction or exchange of the complexed metal with other biomolecules. This requires that the chelating molecule contain at least two sulfhydryls that are one extended arms that allow for extended freedom of rotation and movement of the sulfhydryls so that the most stable orientiation for binding the heavy metal can be obtained. For example, the ideal chelating compound must have degrees of freedom of rotation and movement of the sulfur bonds to be able to bind different heavy metals that have different coordination chemistries (e.g. different bond angles that confer tighter bonding). For example, Hg2+ and Pb2+ both can form two bonds with —SH groups, but the most stable binding of each metal would have different bond angles.
To be effective at treating both intracellular heavy metal toxicity and radiation toxicity as well as oxidative stress associated therewith, the treating compound has to be able to cross the cellular membrane with efficiency and, if the brain is involved, the treating compound must be able to cross the blood brain barrier. In order to be able to do this the compound has to be quite hydrophobic in nature in order to be able to pass through the lipid bilayer of the cell membrane to reach the site of heavy metal binding and intercept the ROS produced by the mitochondria before they react and damage cellular constituents. Further, the ideal treating compound must be of very low toxicity to cells and not disrupt membranes or biological pathways and it should not be involved in any natural metabolism that would destroy its physical character. In addition, the treating compound must be efficiently excreted from all tissues of the body in a non-toxic form. For example, if the treating compound binds mercury cation (Hg2+) it must carry this metal ion out of the body and not distribute it to other organs such as the kidney.
The ideal treatment compound must also exhibit stability to air oxidation and breakdown so that the treating compound can be effectively stored and packaged for delivery to the patient in original, active form. The treating compound ideally must also be suited for ease of administration to a patient. Further, the treating compound must not deplete the body of essential metals such as zinc and copper. In addition, it should also have an adequately long plasma half-life such that it is possible to take eight hours rest and not have the treating compound significantly depleted from the plasma and tissues.
The present invention relates to methods of supplementing the diet of a mammal, removing heavy metals and other toxins from a mammal and ameliorating undesirable oxidative stress in a mammal using a single molecule with cell membrane penetrating abilities, metal chelation and oxygen radical scavenging properties, and non-toxic character. To aid in intraveneous delivery, some hydrophobic (lipophilic) compounds are made to be hydrophilic by formation of hydrophilic (water soluble) analogs via attachment by disulfide linkages that are converted after delivery by the body's reducing capability back to the hydrophobic state. Other compounds have the reverse ability in that they are delivered as hydrophobic esters and converted intracellular, by well known esterases, into water soluble, hydrophilic compounds that are more excretable through the kidneys.